In various types of machines (such as automatic drilling machines, for example), it is necessary to selectively change the tools in the tool holding mechanism of the machines. This is true, for example, in numerically controlled drilling machines for drilling, for example, different sized holes through a stack or several stacks of printed circuit boards.
During the drilling operation, it is necessary that the drills in the drilling mechanisms be periodically replaced with different sized drills for subsequent drilling operations. Changing of the drills, however, results in inoperative or "down" time of the drilling machine. Accordingly, it is desirable that the drill changing procedure be accomplished as expeditiously as possible.
Of course, numerous attempts have been made to design mechanism which reduce the amount of time required for the drill changing operation.
For example, U.S. Pat. No. 3,795,455 to Kosmowski, is directed to an improved tool holder mechanism (referred to in the Patent as a collet) which facilitates rapid manual replacement of one drill for another. However, the mechanism disclosed in the Kosmowski U.S. Pat. No. 3,795,455 is not entirely satisfactory since it requires manual operation in order to change the tools (i.e., the drills) in the apparatus.
Numerous attempts have also been made to design automatic tool changers. For example, see U.S. Pat. Nos. 3,458,924; 3,546,774; 3,566,516; 3,646,664; 3,672,691; 3,709,623; 3,780,423; and 3,803,680. In addition, Excellon Automation Division of Excellon Industries has provided a drill changing mechanism on its Mark III D/E System.
The foregoing-identified drill changing apparatuses may generally be characterized as being highly complex and/or relatively inefficient in operation. Thus, none of the prior art drill changing apparatuses has fulfilled the need for a relatively simple, relatively inexpensive, efficient and effective drilling changing mechanism.